Rubidium and Cesium Systems

CIDEP and CIDNP in Metal and Metallorganic Systems. To date, very few CIDEP studies of metal systems have been reported (139). These included the earlier study of rubidium and cesium systems... 

Since rubidium and cesium hydroxides are most active in catalyzing the conversion of ketoxime to the corresponding pyrrole (3) [89KGS770] it might be supposed that the additives of salts of these metals to the KOH/ DMSO system would increase the catalytic activity of the latter because of exchange processes ... 

Salting-Out Effect Owing to Potassium Chloride. Kobzev (I) maintained, in a study of salts of potassium, sodium, lithium, rubidium, and cesium (all in aqueous solutions), that the solubility of a salt in water was related to its salting-out effect. He found that salts with the solubility from 6.4 to 2.8 g equiv wt per 100 mL of water at 25°C caused stratification in all systems except water-methanol and water-ethanol. Salts with solubilities below 2.82 g equiv wt did not cause salting-out. 

The other alkali metals have been less extensively studied. The propagation rates of polystyrylsodium, -potassium, -rubidium and -cesium have been measured in benzene and cyclohexane [72, 73]. The sodium compound still shows half order kinetics in active centre concentration and is presumably associated to dimers. The rates for the rubidium and cesium compounds are directly proportional to the concentrations of the active chains which are presumably unassociated in solution. Absolute kp values can be determined from the propagation rate in this case. Poly-styrylpotassium shows intermediate behaviour (Fig. 11), the reaction order being close to unity at a concentration of the potassium compound near 5 x 10 M and close to one half at concentrations around 10" M. It could be shown by viscosity measurements that association was absent in the low concentration range. In this system both K2 and kp can be measured. The results are summarized in Table 2. The half order reactions show a large increase in kpK between lithium and potassium which... 

M2F2-Srp2 (M = Li, Na, K). All three binary systems are the simple eutectic. Also in the same series of strontium chlorides, there are only simple eutectic systems for lithium, sodium, and potassium, but systems containing bigger rubidium and cesium cations with low polarization ability already form binary compounds. 

In the systems of subgroup A-2, cathodic reduction of a cation is thermodynamically disadvantageous, as a rule, for the salts of lithium, rubidium, and cesium, in whose solutions solvated electrons can be generated. In sodium salt solutions electrodeposition of the metal takes place. Potassium salt systems occupy an intermediate position. 

Rubidium and cesium are used in very accurate clocks. These clocks have been used to test phenomena predicted by general relativity theory, to investigate changes in the frequencies of pulsars, to track missiles and satellites, and to maintain the extremely accurate time-keeping required by global positioning systems. 

Chemical lasers are pumped by reactive processes, whereas in photodissociation lasers the selective excitation of certain states and the population inversion are directly related to the decomposition of an electronically excited molecule. Photolysis has been the only source of energy input employed in dissociation lasers, although it appears quite feasible to use other energy sources, e.g. electrons, to generate excited states. Table 4 lists the chemical systems where photolysis produces laser action. It is appropriate to begin the discussion of Table 4 with the alkali-metal lasers since Schawlow and Townes in 1958 35> chose the 5 f> 3 d transitions of potassium for a first numerical illustration of the feasibility of optical amplification. These historical predictions were confirmed in 1971 by the experimental demonstration of laser action in atomic potassium, rubidium and cesium (Fig. 14). 

In addition to the relatively conglomerate structures of the potassium, rubidium, and cesium polymers, there are other characteristics of these polymers, or polymer systems, which may make them unsuitable for practical development as rubbers. The molecular weight of the polymer in these systems decreases as the electropositivity of the metal catalyst increases. Thus, all rubidium and cesium polymers produced so far have been very low in molecular weight. Other disadvantages are the high cost and the safety hazard connected with the use of these metals. 

The same type of reactions occur inside the fuel elements of nuclear reactors, where the two alkali metals rubidium and cesium are present as fission products. For instance, in the cesium-uranium-oxygen system two compounds, namely CS2UO4. or Cs2U40,2, are existent. In contact with liquid cesium, only CS2UO4 is stable. In case of absence of cesium metal in the reaction mixture, the other uranate can also be formed... 

The principal commercial source of rubidium is accumulated stocks of a mixed carbonate produced as a byproduct in the extraction of lithium salts from lepidohte. Primarily a potassium carbonate, the byproduct also contains ca. 23 wt.% rubidium and 3 wt.% cesium carbonates. The primary difficulty associated with the production of either pure rubidium or pure cesium is that these two elements are always found together in nature and also are mixed with other alkali metals because these elements have very close ionic radii, their chemical separation encounters numerous issues. Before the development of procedures based on thermochemical reduction and fractional distillation, the elements were purified in the salt form through laborious fractional crystallization techniques. Once pure salts have been prepared by precipitation methods, it is a relatively simple task to convert them to the free metal. This is ordinarily accomplished by metallothermic reduction with calcium metal in a high-temperature vacuum system in which the highly volatile alkali metal is distilled from the solid reaction mixture. Today, direct reduction of the mixed carbonates from lepidolite purification, followed by fractional distillation, is perhaps the most important of the commercial methods for producing rubidium. The mixed carbonate is treated with excess sodium at ca. 650 C, and much of the rubidium and cesium passes into the metal phase. The resulting crude alloy is vacuum distilled to form a second alloy considerably richer in rubidium and cesium. This product is then refined by fractional distillation in a tower to produce elemental rubidium more than 99.5 wt.% pure. 

From these two main groups of the Periodic System of Elements, only the elements bromine, iodine, rubidium and cesium are produced by nuclear fission to an extent worth mentioning. Iodine and cesium are of particular interest during plant normal operation as well as in accident situations, because of their comparatively high fission yields, their enhanced mobility in the fuel at higher temperatures and the radiotoxicity of some of their isotopes. Both elements are often summarized under the term volatile fission products their similar properties justify their treatment in the same context, despite pronounced differences in their basic chemical behavior. 

This volume presents and evaluates solubility data for the orthophosphates of lithium, sodium, potassium, rubidium and cesium. There are two exceptions to this (a) data are presented for the solubility of sodium metaphosphate in water (1) on page 46 in chapter 3 and (b) solubility values for the system (2) are given on... 

The various systems are treated in the order in which the alkali metals are listed in Group I of the Periodic Table. Most of the available solubility data are for the orthophosphates of sodium and potassium, and for these two systems an introductory chapter on the M0H-HjP0 -H20 (M = Na or K) system is given. Each of these chapters (chapters 2 and 7) also refers to compounds to be considered in later chapters. Following each of these introductory chapters there are chapters dealing with the solubility data for individual orthophosphates having different M/P ratios, and the ternary and multicomponent systems in which these orthophosphates are components. Only one chapter is devoted to each of the orthophosphates of lithium, rubidium and cesium. 

The reduced plots for rubidium and cesium coincide accurately, suggesting that a law of corresponding states is valid for these two members of the alkali group. The curves for the alkali metals are, however, extremely asymmetric and therefore quite different from those of argon and xenon. The diameters exhibit strong curvature over substantial temperature ranges. Asymmetric coexistence curves are a common characteristic of fluid systems that show a MNM transition under variation of the conduction electron concentration. The metal-ammonia solutions (Chieux and Sienko, 1970) and electron-hole liquid (Thomas et al., 1978)... 

For the group I metals, it was found that stable complexes beween dicyclohexyl-18-crown-6 and sodium, potassium, rubidium and cesium metals have been obtained in benzene. These new complexes demonstrated the ability to act as active catalysts for the polymerization of butadiene and isoprene. Such catalysts increased the yield and rate of polymerization as compared with conventional alkali metal anionic systems. In addition, the microstructure of the polymer is different from that of the same polymer prepared by metals alone. 

Ternary triphosphates form in the system RCl3-Na5P30jo-H20 when concentrations are suitable (Petushkova et al., 1971). In systems containing rubidium and cesium the composition (Rb, Cs)RHP30io (R = Pr Er), corresponding to the dihydrogen compound, is formed at 200°C (Vinogradova and Chudinova,... 

Samuseva RG, Oknnev YA, Plyushchev VE (1967) Binary systems from chromates and dichromates of potassium, rubidium, and cesium. Zh Neorg Khim 12 2822-2824... 

Later, they revisited their prototypical catalyst system. After a series of screening of the metal (Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba), sodium and potassium L-prolinate were found more effective than the lithium salt. Rubidium and cesium salts enhanced the stereoselectivity. Increasing the size of the ester group of the malonate resulted in a higher... 

In 1863 R. C. Bottger of Frankfort-on-the Main found that thallium occurs in some spring waters. A certain salt mixture from Nauheim contained, in addition to the chlorides of sodium, potassium, and magnesium, those of cesium, rubidium, and thallium. Since he was able to prepare a thallium ferric alum exactly analogous to potassium ferric alum, he regarded thallium as an alkali metal (72, 73). Although it is sometimes univalent like sodium and potassium, it is now classified in Group III of the periodic system. 

Rubidium alloys easily with potassium, sodium, silver, and gold, and forms amalgams with mercury. Rubidium and potassium arc completely miscible 111 the solid state. Cesium and rubidium form an uninterrupted series of solid solutions. These alloys, in various combinations, are used mainly as getters for removing the last traces of air in htgh-vacmim devices and systems. 

A recent paper (6) reports an interesting case of a felspathoid, cancrinite, previously obtained in typically sodic environments with (7) or without added salts ( 8), synthesized in bicationic systems formed by lithium and a large alkaline cation (rubidium or cesium). Such syntheses suggest that cancrinite is a further phase, the... 

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